Various types of foregoing motors are required to rotate with high accuracy, at high speed and with low noise, and to be manufactured at low cost. A bearing for supporting a spindle of the motor is one of elements to determine these required performances, so that a dynamic pressure bearing having characteristics superior in the above required performances is considered to be used, or is actually used as this type of bearing, in recent years.
A dynamic bearing device installed in a spindle motor of a disc device such as HDD and the like, for example, is provided with a radial bearing portion for rotatably supporting an axial member in a non-contact manner in a radial direction, and a thrust bearing portion for rotatably supporting the axial member in a non-contact manner in a thrust direction, and the radial bearing portion utilizes grooves for generating dynamic pressure (dynamic pressure generating grooves) formed in the inner peripheral surface of a bearing sleeve, or in the outer peripheral surface of the axial member. The thrust bearing portion utilizes, for example, a dynamic pressure bearing in which dynamic pressure generating grooves are formed in the both end faces of a flange portion of the axial member, or in faces opposed thereto (the end face of the bearing sleeve, the end face of a thrust member fixed in a housing, and the like) (refer to, for example, Japanese Patent Laid-Open Publication No. 2000-291648).
Generally, the bearing sleeve is fixed on a predetermined position of the inner periphery of the housing, and in most cases, a seal member is disposed in an opening of the housing to prevent lubricating oil injected into the internal space of the housing from leaking outside.
In the dynamic bearing device having the above structure which comprises the housing, the bearing sleeve, the axial member, the thrust member, and the seal member, an effort is under way to increase accuracy in finishing each part and in assembling them, for the purpose of ensuring high bearing performance necessary in accordance with highly increase in performance of information-processing equipment. In this type of dynamic bearing device, on the other hand, cost reduction is highly demanded in accordance with the downward trend of the price of the information-processing equipment.
Increase in efficiency of an assembly process is one of key factors in the cost reduction of this type of dynamic bearing device. In other words, the housing and the bearing sleeve, the housing and the thrust member, and the housing and the seal member are secured to each other with adhesive in general, but using adhesive is a cause of decrease in efficiency of the assembly process, because it takes relatively long time for applying and solidifying the adhesive. The possibility of outgas generation due to the adhesive and the deterioration of adhesion with a lapse of time are feared too.